Merge branch 'develop' into feature/test-nan-op-gte
add NaN test for operator_greater_than_or_equal
added NaN test for logical_gte
added NaN test for op_gte
added doc for operatore_gte
Merge branch 'develop' into feature/test-nan-op-gte
Merge pull request #1007 from stan-dev/feature/test-nan-op-gte

Feature/test nan op gte